Heat the oven to 350 degrees. Grease a small baking pan (a square baking dish of 8x8 or 9x9 inches will do).
In a pot, melt the butter and mix in the flour.
Cook the sauce over low heat until it becomes smooth and starts boiling, stirring occasionally with an electric mixer.
Lower the heat and gently mix in 1 cup of cheddar cheese.
Place half of the sliced potatoes in the baking dish.
Put half of the cheese sauce on the potatoes.
Do the same thing with the next layer of potatoes and cheese sauce.
Put half a cup of cheddar cheese on top. Sprinkle a bit of paprika on top for color.
Cook in the oven at 350°F or higher for around 1 hour until the potatoes are soft.
Have fun!